A gas turbine engine generally includes a fan and a core arranged in flow communication with one another. Additionally, the core of the gas turbine engine generally includes, in serial flow order, a compressor section, a combustion section, a turbine section, and an exhaust section. In operation, air is provided from the fan to an inlet of the compressor section where one or more axial compressors progressively compress the air until it reaches the combustion section. Fuel is mixed with the compressed air and burned within the combustion section to provide combustion gases. The combustion gases are routed from the combustion section to the turbine section. The flow of combustion gases through the turbine section drives the turbine section and is then routed through the exhaust section, e.g., to atmosphere.
Combustion gas temperatures are relatively hot, such that some components in or near the combustion section and the downstream turbine section require features for deflecting or mitigating the effects of the combustion gas temperatures. For example, one or more heat shields may be provided on a combustor dome to help protect the dome from the heat of the combustion gases. However, combustion gases can leak around the heat shields and impinge on the combustor dome, which can reduce an amount of working fluid for driving the turbine section as well as thermally damage the combustor dome. Moreover, the heat shields may be fabricated from a non-traditional high temperature material, such as a ceramic matrix composite (CMC) material, and the dome fabricated from a metallic material, such that there is a coefficient of thermal expansion (CTE) mismatch or different thermal growth between the components. As the metallic dome expands, the CTE mismatch can drive larger gap openings between CMC heat shield segments, e.g., compared to gap openings between metallic heat shields, and thereby encourage leakage as well as expose the dome.
In some typical combustor designs, a seal may be provided between a heat shield and the dome, but the dome can still be exposed in gaps between heat shields. Commonly, a flow of cooling fluid (i.e., purge flow) is directed against the dome in areas prone to leakage, such as gaps between heat shield segments, but diverting cooling flow to purge the leakage areas can negatively impact turbine emissions. Further, turbine performance and efficiency generally may be improved by increasing combustion gas temperatures. Therefore, there is an interest in providing heat shields formed from high temperature materials, such as CMC heat shields, that can withstand increased combustion gas temperatures yet also require less cooling, to increase turbine performance and efficiency while also reducing turbine emissions.
Accordingly, combustor heat shields and combustor assemblies that overcome one or more disadvantages of existing designs would be desirable. In particular, a combustor assembly utilizing CMC heat shields and seals that extend between adjacent CMC heat shields would be beneficial. Additionally, a combustor assembly that minimizes purge flow in an area of a combustor dome and heat shield interface would be useful. Further, a sealing mechanism that compensates for CTE mismatch between combustor heat shields and a combustor dome would be advantageous.